1. Field of the Invention
The present invention relates to a process for continuous refining of oils and fats by continuously contacting crude oils and fats with a lower alcohol in the presence of an acid catalyst. More particularly, the present invention relates to a process for continuous refining of crude oils and fats containing free fatty acids and impurities by removing the impurities prior to interesterification thereof with a lower alcohol, characterized in that the oils and fats are continuously contacted with the lower alcohol in the presence of the acid catalyst under special operation conditions in a special reaction device.
2. Description of Prior Arts
Lower alcohol esters of fatty acids are widely used as starting materials of higher alcohols by catalytic reduction thereof and also as starting materials of surfactants. They are produced generally by an interesterification method between oils or fats and the lower alcohol or by an esterification method wherein fatty acids obtained by the hydrolysis of oils or fats are esterified with a lower alcohol. For the production of the lower alcohol esters of fatty acids on an industrial scale, there has been employed generally a method wherein the oils and fats are interesterified with a lower alcohol in the presence of an alkali catalyst.
The crude oils and fats used as the starting materials generally contain impurities such as polypeptides and phospholipids in addition to about 2-5% of free fatty acids, though the impurities are various depending on kinds of the oils and fats. If those oils and fats are subjected directly to the interesterification, an alkali used as interesterification catalyst is consumed by the free fatty acids contained therein and, therefore, the interesterification reaction does not proceed sufficiently unless the alkali is supplemented in a large amount. Further, oils and fats dissolved in glycerol layer are increased in amount by emulsification and solubilization effects of resulting fatty acid soaps. Thus, problems are posed such as deterioration of qualities of the esters and by-produced glycerol and increase of loss.
For solving those problems, there have been employed following methods (1)-(3) wherein purification is effected to remove impurities such as free fatty acids from the reaction system prior to the interesterification step and following methods (4) and (5) wherein a special step is employed, in order to carry out the interesterification reaction of oil or fat with a lower alcohol in the presence of an alkali catalyst at a relatively low temperature of, for example, below 100.degree. C.